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User blog:KaptainWombat/Mediterranean Basin: 6 MyF
Today, the Mediterranean is an almost landlocked ocean basin, the last large remnant of the Tethys Ocean. But several million years ago, it was a toxic lake of salt more than 2 km below sea level, where only brine flies and microbes could live long term. But this was not to last, some 100,000 years after it was first isolated, the entire basin was flooded in only a few years when the Atlantic broke through at Gibraltar, in a flood that is believed to have been one of the largest in the earths history. But as Africa continues to slowly move northwards, it seems inevitable that this will happen again. In some 6 million years time, at the height of the 'EPIA' (Early Postocene Ice Age) the combination of low sea levels and the closing of the Gibraltar Straits has repeated the saltbowl event. Unlike the Miocene event, however, this event lasts not for 100,000 years, but for almost 3 million years, and due to the dry ice age climate and high mountains surrounding the basin, there is almost no rain, though there are still several rivers that flow into the area, mostly from the still filled Black Sea basin. This extremely dry climate means that almost no mammals live here, and all are small. The largest animal is a reptile known as the Theros Lizard, which is able to grow up to almost 5 metres long in the hot climate and absense of mammalian competition. There are also large birds of prey, similar to those that live in dry areas today, known as Hawkrows, which haunt the former islands, which are now tall mountains relative to the vast salt plain around them. Several of these mountains are active volcanoes, which periodically spread ash over the basin. Geology Due to the long time that the Mediterranean was isolated from the rest of the worlds oceans, the geology and climate of the basin is rather different from the shorter saltbowl episodes preceding it. Volcanism All the Mediterranean volcanoes active today are long extinct by 6 MyF, but the complex tectonic forces responsible still cause numerous large earthquakes, and new volcanoes to erupt, The loss of the sea has depressurised the crust and fuelled impressively large lava eruptions. The centre of activity is the enormous volcano of Mt Knossos, named after an ancient city on modern Crete, which was destroyed by a volcanic tsunami around 1500 BCE. Mt knossos, like the modern volcanoes of the region, is built along an ark through what is today the Agaean Sea, and the caldera of the volcano is situated between the greek mainland and what was once Crete. Mt Knossos is fuelled by the subduction of the African plate under Europe, but unlike most similar situations, the subduction trench is not underwater. Water is the main driver of subductive volcanism, so the eruptions are typically* less explosive. The subduction of evaporite sediments also enriches the magma with Sulfur compounds, and alkali metals, resulting in unusually alkaline magma compositions. Mt Knossos itself is a cluster of lava domes built on top of a massive complex shield volcano, the largest active volcano to exist on the planet at the time, measuring almost 150 km wide along its longest axis. As the colossal mountain grew, magma began to accumulate in a large shallow magma chamber, before the main central volcano fell dormant for close to 30,000 years, before erupting in a VEI 7 eruption which, due to the abundance of sulfur and halogens, was one of the most damaging eruptions of the immediate future. This eruption changed global climate, and lead to the extinction of some species of animals, particularily birds. the eruption formed a massive caldera over 20 km in diemeter. Post caldera eruptions formed another smaller volcano inside its caldera, which, since its formation, has been erupting alkali basalt lava which has formed a tall pyroclastic cone, and a vast lava field, with some lava flows reaching over 120 km from their sorces on the flanks of the main volcano. The summit of this volcano, despite it being built on a base that is below sea level, is some 3000 metres in altitude, and is covered in patches of snow for most of the year, although the arid climate prevents glaciers from forming. Animals Animals are rare in the toxic salt basin. But a variety of things live in the much more habitable 'highlands' surrounding the former sea. The extremely low elevation of the basin also results in unusually dense air, meaning a variety of strange flying creatures exist in the basin to share the skies with the birds. Reptiles Several species of unique reptiles call this basin home, as only reptiles can retain water efficiently in the dry salty climate. Theros Lizards, Varanagama sp. The theros lizards, or varanagamas include some of the largest reptiles in Eurasia, and are distant descendants of modern European agamas. There are many species of theros lizards throughout southern Europe, though most are rather small and are little different from their modern day ancestors. One noticable difference is the notorious Varanagama gigantea, or Polyphemus Lizard. Named because of a prominent black false eye on the top of its head, this dinosaur of a creature can be almost 5 metres long, when counting its long tail. In appearance it resembles, slightly, its distant modern Australian relative, the well known Frill-Neck Lizard. To minimise contact with the burning hot salt and sand, and from the sun itself, the lizard is almost ghostly white, and runs on its hind legs. The tail of this species is banded black and white. Flizard, Volagama monotypica. The flizard is a small lizard species that, like some today, can glide on skin extensions, though the lizards have been observed making short powered flights to get airborne, though this seems to have been a 'discovered' thing. Its 'wings' are really webs of skin between its somewhat elongated fingers, and between its ribs, similar to the modern Draco lizards, and to gliding geckos, though their gliding abilities are considerably better. The flizard is most likely a once off evolutionary event, as there is only one species, though it is believed to be closely related to theros lizards, and to modern agamas. When on the ground where it spenrd most of its time, flizards are hard to distinguish from the other small specialised lizards that it shares its habitat with, however all flizards have a black head, which is used to warm them up quicker on account of their aerobatic abilities. Birds With the dense air in the lower reaches of the basin, flying birds are able to get huge with minimal effort. Hawkrow, Barocorvus kronos. Hawkrows are large birds of prey descended from modern Eurasian ravens, and they locally fill the niches of more conventional birds of prey. Due to the dense atmosphere, these birds are the heaviest flying birds in earths history. Flamega, Phoenicopterus giganteus. Mammals Category:Blog posts